The present invention relates to a pressurized vessel, bottle, container or the like for the storage and supply of noble gas, special gas, blends or mixture of gases particularly of the kind required to exhibit a high degree of purity; and more particularly the invention relates to a pressure vessel of such a type which includes a bottom, a jacket, or main part and head part with a neck portion provided for receiving a valve to be covered by a protective cap. Vessels of the type to which the invention pertain, moreover, require a configuration readily admitting treatment of the interior surface for eliminating any surface roughness.
Generally speaking the electronic industry and other fields of art employ certain gases during production and for certain production purposes and phases a gas or gases of a high degree of purity is required. These gases have to be stored and are usually transported in steel flasks, bottles, vessels, containers etc. but it was found that here there may be certain contamination i.e. impurities that enter the gas filled interior of the bottle to have the effect of changing the concentration of the components. These impurities may render questionable from some point onwards further utilization of the stored gas. These conditions are particularly important in the semiconductor field and involve corrosive combustible gases.
Generally speaking it it known that the surface roughness as well as the cleanliness of the interior surface of such a pressure vessel is a direct factor for maintaining the purity and the stability of the mixture or blend of the gas stored in that vessel. Moreover, the material itself used for the bottle, vessel, flask or container has a certain influence on maintaining purity of its content. For economic reasons it is required that during transport as well as storage the gases are stored at a high pressure which is to be maintained. This in turn requires that a material for the container, flask or bottle be used which has sufficient strength to withstand the high pressure. Strength requirements are fulfilled by the usual steel bottles including unalloyed or low alloyed steel. On the other hand these bottles in accordance with the state of the art no longer suitable for the now required degrees of purity and corrosion resistance.
Generally speaking it has been recognized that the gas impurity content is reduced the lower the internal surface roughness of the container. Hence smoothing the surface is a direct factor that eliminates, to some extent at least, long term impurity growth in the container. In order to provide as smooth an interior surface as possible German printed patent application 23 64 377 proposes to electrolytically tin plate such a bottle in its interior or to provide for a zinc plating process, assuming that the container is made of ferritic pertitic steel. In another publication it has been suggested to blast the interior surface with quartz balls or globules and to clean it chemically or with ultrasound.